Chapter 38 Pt. II Human Diseases Caused by Bacteria
Arthropod-Borne Diseases generally rare some are of historical interest some newly emerged
Yersinia pestis nonenteric tiny, gram-negative rod, unusual bipolar staining & capsules virulence factors capsular & envelope proteins protect against phagocytosis & foster intracellular growth coagulase, endotoxin, murine toxin
Yersinia pestis
Yersinia pestis humans develop plague through contact with wild animals (sylvatic plague) or domestic or semidomestic animals (urban plague) or infected humans found in 200 species of mammals rodents without causing disease flea vectors bacteria replicates in gut, coagulase causes blood clotting that blocks the esophagus; flea becomes ravenous
Plague clinical manifestations subcutaneous hemorrhages, fever, and buboes (hence name bubonic plague) high mortality if untreated pneumonic plague arises from: primary exposure to infectious respiratory droplets of infected persons or cats secondary to hematogenous spread in a patient with bubonic plague
Plague Yersinia pestis proliferates inside phagocytic cells Figure 38.9 (a)
Plague Yersinia pestis causative agent Figure 38.9 (b) and (c)
Plague diagnosis made in reference labs which use direct microscopic examination, culture and serological tests, and PCR treatment, prevention, and control antibiotic therapy ectoparasite and rodent control, isolation of human patients, prophylaxis of exposed persons, immunization of persons at high risk
Food-Borne and Water-Borne Diseases gastroenteritis is most common food poisoning food source of pathogen food-borne infection pathogen must colonize host food-intoxication ingestion of toxin enterotoxins disrupt functioning of intestinal mucosa causing nausea, vomiting, and/or diarrhea generally prevented and controlled by sanitation measures
Campylobacter jejuni Gastroenteritis Campylobacter jejuni is a gram-negative curved rod found in intestinal tract of animals (e.g., chickens, turkey, and cattle) causes campylobacteriosis transmitted to humans by contaminated food or water, contact with infected animals or anal-oral sexual activity C. jejuni invades epithelium of small intestine, causes inflammation and secretes an endotoxin
Campylobacter jejuni Gastroenteritis diagnosis culture in low oxygen, high CO 2 atmosphere treatment, prevention, and control symptomatic/supportive therapy and antibiotic therapy in severe cases good personal hygiene, safe food handling practices
Cholera caused by Vibrio cholerae, a comma-shaped, gram-negative bacterium acquired by ingesting food or water contaminated by fecal matter from patients or carriers shellfish are natural reservoirs organisms adhere to intestinal mucosa of small intestine and secrete the toxin choleragen
Figure 38.24
Cholera presence of toxin results in massive loss of water and electrolytes production of rice-water stools diagnosis culture from feces with subsequent identification by agglutination reactions treatment, control and prevention oral rehydration antibiotic therapy
Clostridium gram-positive, spore-forming rods anaerobic & catalase negative 120 species oval or spherical spores produced only under anaerobic conditions synthesize organic acids & alcohols & exotoxins cause wound & tissue infections & food intoxications
Clostridium perfringens causes gas gangrene in damaged or dead tissues 2 nd most common cause of food poisoning, worldwide virulence factors toxins alpha toxin causes RBC rupture, edema & tissue destruction collagenase hyaluronidase DNase
Gas Gangrene or Clostridial Myonecrosis most commonly caused by Clostridium perfringens gram-positive, spore-forming rod produce gas gangrene, a necrotizing infection of skeletal muscle or clostridial myonecrosis secretes toxin and tissue damaging enzymes transmitted by contamination of injured tissue by spores from soil or bowel microbiota
Gas gangrene clinical manifestations severe pain, edema, drainage, and muscle necrosis diagnosis recovery of appropriate clostridial species and characteristic disease symptoms treatment, prevention, and control surgical debridement, administration of antitoxin, antibiotic therapy, and hyperbaric oxygen therapy prompt treatment of all wound infections and amputation of limbs
Figure 38.11
Clostridium perfringens treatment of gangrene debridement of diseased tissue large doses of cephalosporin or penicillin hyperbaric oxygen
Clostridium botulinum Causes 3 diseases 1. food poisoning -spores are in soil, may contaminate vegetables; improper canning does not kill spores & they germinate in the can producing botulinum toxin toxin causes paralysis by preventing release of acetylcholine 2. infant botulism caused by ingested spores that germinate & release toxin 3. wound botulism spores enter wound & cause food poisoning symptoms
Botulism caused by Clostridium botulinum, an obligately anerobic, endospore-forming, gram-positive rod on Select Agent List most common source of infection is insufficiently heated home-canned food endospores not killed, then germinate and produce toxin if food inadequately cooked, toxin remains and causes disease
Figure 38.23
Botulism infant botulism endospores ingested, germinate, reproduce, and produce exotoxin constipation, listlessness, general weakness, and poor appetite; death may result from respiratory failure treatment, prevention and control symptomatic/supportive therapy and administration of antitoxin safe food processing practices and not feeding honey to babies under one year of age
Clostridium tetani common resident of soil & GI tracts of animals causes tetanus or lockjaw, a neuromuscular disease spores usually enter through accidental puncture wounds, burns, umbilical stumps, frostbite, & crushed body parts tetanospasmin neurotoxin causes paralysis vaccine booster needed every 10 years
Clostridium difficile normal resident of colon, in low numbers causes antibiotic-associated colitis treatment with broad-spectrum antibiotics kills the other bacteria, allowing C. difficile to overgrow produces enterotoxins that damage intestine major cause of diarrhea in hospitals
Salmonella motile; ferments glucose resistant to chemicals bile & dyes S. typhi typhoid fever ingested bacilli adhere to small intestine, cause invasive diarrhea that leads to septicemia 2 new vaccines S. cholerae-suis - pigs S. enteritidis 1,700 serotypes- salmonellosis zoonotic gastroenteritis 2-5 days
sepsis Sepsis and Septic Shock systemic response to a microbial infection e.g., changes in heart rate, respiratory rate, and blood cell counts septic shock sepsis associated with severe hypotension can be caused by gram-positive bacteria, fungi and endotoxin-containing gram-negative bacteria 38
Salmonellosis caused by >2,000 Salmonella serovars, gram-negative non-spore forming rods transmitted to humans by contaminated foods such as beef products, poultry, egg products, and water disease results from food-borne infection bacteria in intestinal mucosa produce enterotoxin and cytotoxin
Salmonellosis symptoms include abdominal, pain, cramps, diarrhea, nausea, vomiting and fever diagnosis isolation of organism from food or patients stools treatment, control and prevention fluid and eletrolyte replacement good food handling practices, proper refrigeration, adequate cooking
Typhoid Fever caused by Salmonella enterica subspecies enterica serovar typhi a gram-negative rod acquired by ingestion of food or water contaminated by feces in infected humans or person-to-person contact paratyphoid fever milder form of disease
Typhoid Fever bacteria spread from small intestine to lymphoid tissue, blood, liver and gallbladder symptoms include fever, headache, abdominal pain, anorexia and malaise in carriers (e.g., Typhoid Mary) bacteria grow in gallbladder and reach intestine through bile duct
Typhoid Fever diagnosis demonstration of typhoid bacilli in blood, urine, or stools serology (Widal test) treatment, prevention and control antibiotic therapy vaccine for high risk individuals purification of drinking water, prevention of food handling by carriers, and isolation of patients
Shigellosis bacillary dysentery caused by four species of genus Shigella gram-negative, non-spore forming rods organisms cause inflammatory reaction in mucosa humans are the only host
Shigella shigellosis incapacitating dysentery S. dysenteriae, S. sonnei, S. flexneri & S. boydii produce H 2 S or urease invades villus of large intestine, can perforate intestine or invade blood enters Peyer s patches instigates inflammatory response; endotoxin & exotoxins treatment fluid replacement & ciprofloxacin & sulfa-trimethoprim
Shigellosis endotoxins and exotoxins may play role in disease progression watery stools often contain blood, mucus and pus diagnosis biochemical characteristics serology treatment, prevention and control antibiotic therapy prevention by use of good personal hygiene and a clean water supply
Traveler s Diarrhea and Escherichia coli infections traveler s diarrhea caused by certain viruses, bacteria, or protozoa normally absent from traveler s environment E. coli is one of major causative agents six categories or strains are recognized
Traveler s disease diagnosis past travel history and symptoms, isolation and identification of causative agents using DNA probes, tests for virulence factors, and PCR treatment, prevention, and control symptomatic/supportive therapy and antibiotic therapy avoiding contaminated food and water
a. enterotoxic b. enteroinvasive c. enteropathogenic or attaching-effacing d.enterohemorrhagic e. enteroaggregative f. diffusely adhering Figure 38.25
Pathogenic E. coli Strains enterotoxigenic E. coli (ETEC) produces one or both enterotoxins responsible for diarrhea distinguished by their heat stability enteroinvasive E. coli (EIEC) multiplies within intestinal epithelial cells may produce a cytotoxin and an enterotoxin enteropathogenic E. coli (EPEC) causes effacing lesions caused by destruction of brush border microvilli on intestinal epithelial cells 52
Figure 38.30 53
More diarrheagenic strains enterohemorrhagic E. coli (EHEC) produces effacing lesions, leading to hemorrhagic colitis releases shiga-like toxins implicated in hemolytic uremic syndrome and thrombotic thrombocytopenic purpura e.g., E. coli 0157:H7
More strains enteroaggregative E. coli (EAggEC) forms clumps adhering to epithelial cells toxins have not been identified diffusely adhering E. coli (DAEC) adheres in a uniform pattern to epithelial cells particular problem in immunologically naïve or malnourished children